1) I mean Business.

我是当真的。
3) Do you really mean it?

说的可是当真?
4) He means what he says, ie is not joking, exaggerating, etc.

他说话是当真的.
5) What I say is true.

我所说的是真的。
6) I know that is true.

我知道那是真的。
参考词条